In a non-aqueous electrolyte secondary battery, use of a phosphorus-containing compound has been known, for suppressing an exothermic reaction between the positive electrode active material and the non-aqueous electrolytic solution. Patent Document 1 discloses suppressing the exothermic reaction between the positive electrode active material and the non-aqueous electrolytic solution by dissolving a phosphate ester at 15% or more by mass based on the total amount of the non-aqueous electrolytic solution. In addition, in Patent Document 2, it is disclosed that the exothermic reaction between the positive electrode active material and the non-aqueous electrolytic solution is suppressed by adding polyphosphoric acid, a phosphazene derivative, or the like in the positive electrode mixture at 6% or more by mass.